The present invention generally relates to semiconductor devices, and more particularly to a memory cell that uses a negative differential resistance of RHET and a memory device that uses such a memory cell.
Semiconductor memories are used extensively as essential element of computers and other microprocessors. In order to increase the storage capacity, various efforts have been made for increasing the integration density of the semiconductor memory devices. Generally, a dynamic random access memory (DRAM), a typical example of the semiconductor memory device, uses a FET for storing information. Although the dynamic random access memory can be constructed to have an extremely small size, the necessity of periodical refreshment for retaining the information substantially deteriorates the access speed of the device.
On the other hand, there is a so-called static random access memory (SRAM) that stores information as a result of the flip-flop operation of transistors. This type of memory device does not require refreshing and hence provides a very fast access speed. Thus, the device is used extensively for cache memories that require a particularly high access speed. On the other hand, conventional static random access memory devices use at least six transistors to obtain the desired flip-flop action. Thus, the device inevitably occupies a substantial area and the desired increase in the integration density cannot be achieved easily.